<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="js/21.js"></script>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        .three {
            width: 150px;
            height: auto;
            text-align: center;
            list-style: none;
        }
    </style>
</head>

<body>
    <!-- 外层容器 -->
    <div class="three">
        <!-- 列表 -->
        <ul class="list">
            <li class="item">
                <p>百度</p>
                <ul class="content" style="display: none;">
                    <li>1</li>
                    <li>2</li>
                    <li>3</li>
                </ul>
            </li>
            <li class="item">
                <p>京东</p>
                <ul class="content" style="display: none;">
                    <li>4</li>
                    <li>5</li>
                    <li>6</li>
                </ul>
            </li>
            <li class="item">
                <p>淘宝</p>
                <ul class="content" style="display: none;">
                    <li>7</li>
                    <li>8</li>
                    <li>9</li>
                </ul>
            </li>
        </ul>
    </div>
</body>

</html>